Yes, I am curious about plain AAC files.Ok. Thanx! I'll do some tests, especially what other software supports.Tried Foobar2000, when I click on save it says not supported format. In dbPowerAmp after I edit some fields and click ok/save it just closes and when I open the file again, no tags.Does BASS supports ID3 means ID3v2 too? I am always suggesting ID3v2 because I think it is the most developed tagging system.

But then there's a bug in the AAC add-on. Accidentally I tagged an MP4 file with ID3v2 a couple of days ago and BASS could not open it. Didn't investigate it just remember that it could not be played and it showed up as 0 playtime on my list.

Uploaded file 'Tagged with ID3v2.mp4'.Tried now once again and it seems BASS is processing the file for some seconds but without success.Please inform me if the problem is with the ID3v2 tag, it is created by my ID3v2 Library.

I see what's going wrong. Tagging software will often add some padding (bunch of 0s) after ID3v2 tags to leave room for more tags to be inserted, so BASS will skip any 0s that it finds after the ID3v2 tags to get to the audio data. The problem in this case is that MP4 files start with 3x 0s and they're getting skipped too, which means that the MP4 file structure is no longer valid. I don't think this is a big concern though, as MP4 has its own tagging system and ID3v2 tags don't belong there

But if you wish I can give you a little help to seek to exactly at the ID3v2's end.It's tad simple.Basically if you find and 'ID3' at the start of the file jump 3 bytes, then read 4 bytes 'size' and unsync it and skip that many bytes. And you are at the start of the real audio file.I thought BASS already does this BTW.

Yes, BASS does use the size information from the ID3v2 tag header, but some software adds padding outside of the ID3v2 tag, ie. the ID3v2 header's size information doesn't include the padding. So BASS also looks for padding after the ID3 tag.